Effect of external magnetic field on the critical current in single and bifilar Bi-2223 tapes

We report on measurements of the critical current in a single and bifilar multifilamentary Bi-2223/Ag tapes, at 77 K, under various DC magnetic fields applied perpendicular to the tape plane. At low applied fields the bifilar tape exhibits higher critical current, as expected. However, above ∼50 G the situation is reversed, i.e., the critical current of the single tape is higher. These results are attributed to the different spatial distribution of the self-field in these two configurations. Our data and analysis imply that, in terms of critical current, the bifilar configuration has over advantage over the single tape configuration only in a limited range of external magnetic fields.